MSLRHv01emadicius

Hunt Hypothesis

This YARA rule targets specific memory patterns associated with the MSLRHv01emadicius signature, likely indicating the presence of a low-severity malware implant or script-based payload executing within a host. Proactively hunting for this signature in Azure Sentinel allows the SOC team to identify stealthy, low-noise intrusions that may evade traditional network-based detections and confirm early-stage compromise before lateral movement occurs.

YARA Rule

rule MSLRHv01emadicius
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 EB 05 E8 EB 04 40 00 EB FA E8 0A 00 00 00 E8 EB 0C 00 00 E8 F6 FF FF FF E8 F2 FF FF FF 83 C4 08 74 04 75 02 EB 02 EB 01 81 E8 0A 00 00 00 E8 EB 0C 00 00 E8 F6 FF FF FF E8 F2 FF FF FF 83 C4 08 74 04 75 02 EB 02 EB 01 81 E8 0A 00 00 00 E8 EB 0C 00 00 E8 }
	$a1 = { 60 EB 05 E8 EB 04 40 00 EB FA E8 0A 00 00 00 E8 EB 0C 00 00 E8 F6 FF FF FF E8 F2 FF FF FF 83 C4 08 74 04 75 02 EB 02 EB 01 81 E8 0A 00 00 00 E8 EB 0C 00 00 E8 F6 FF FF FF E8 F2 FF FF FF 83 C4 08 74 04 75 02 EB 02 EB 01 81 E8 0A 00 00 00 E8 EB 0C 00 00 E8 F6 FF FF FF E8 F2 FF FF FF 83 C4 08 74 04 75 02 EB 02 EB 01 81 0F 31 50 0F 31 E8 0A 00 00 00 E8 EB 0C 00 00 E8 F6 FF FF FF E8 F2 FF FF FF 83 C4 08 2B 04 24 74 04 75 02 EB 02 EB 01 81 83 C4 04 E8 0A 00 00 00 E8 EB 0C 00 00 E8 F6 FF FF FF E8 F2 FF FF FF 83 C4 08 3D FF 0F 00 00 EB 01 68 EB 02 CD 20 EB 01 E8 76 1B EB 01 68 EB 02 CD 20 EB 01 E8 CC 66 B8 FE 00 74 04 75 02 EB 02 EB 01 81 66 E7 64 E8 0A 00 00 00 E8 EB 0C 00 00 E8 F6 FF FF FF E8 F2 FF FF FF 83 C4 08 74 04 75 02 EB 02 EB 01 81 0F 31 50 0F 31 E8 0A 00 00 00 E8 EB 0C 00 00 E8 F6 FF FF FF E8 F2 FF FF FF 83 C4 08 }

condition:
		$a0 or $a1 at pe.entry_point
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 2 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: A developer or DevOps engineer uses Visual Studio Code or JetBrains IntelliJ IDEA to edit a large C++ or C# project, causing the IDE’s background indexing service (e.g., devenv.exe or idea64.exe) to spawn temporary worker processes that load specific compiler libraries or debug symbols matching the YARA signature.

  • Filter/Exclusion: Exclude processes where the parent executable is known IDE binaries (devenv.exe, idea64.exe, code.exe) and the working directory resides within standard development folders (e.g., C:\Users\*\Documents\Projects\, C:\dev\).

• Scenario: An automated Windows Server Update Services (WSUS) or SCCM (System Center Configuration Manager) patch deployment task runs on a scheduled basis, triggering the wuauclt.exe or ccmsetup.exe process to download and stage updates. The staging process may temporarily write update packages to disk or load specific DLLs that match the rule’s byte patterns.

  • Filter/Exclusion: Exclude events where the process name is wuauclt.exe, ccmsetup.exe, or ccmexec.exe and the command line contains arguments related to patching, updating, or deployment (e.g., /update, /deploy, /install).

• Scenario: A security team runs a VirusTotal or ESET NOD32 real-time scanning engine on a shared file server. During a full scan, the antivirus engine (navapsvc.exe, esetsvc.exe) opens and reads large binary files (e.g., .dll, .exe) for analysis, potentially loading internal components that trigger the YARA rule due to known benign code patterns.

  • Filter/Exclusion: Exclude processes where the parent or current executable